Stormwater Design: Quantity Control
LEED 2.2 Requirements:
Implement a stormwater management plan that reduces impervious cover, promotes infiltration, and captures and treats the stormwater runoff from 90% of the average annual rainfall* using acceptable best management practices (BMPs).
BMPs used to treat runoff must be capable of removing 80% of the average annual post development total suspended solids (TSS) load based on existing monitoring reports. BMPs are considered to meet these criteria if (1) they are designed in accordance with standards and specifications from a state or local program that has adopted these performance standards, or (2) there exists in-field performance monitoring data demonstrating compliance with the criteria. Data must conform to accepted protocol (e.g., Technology Acceptance Reciprocity Partnership [TARP], Washington State Department of Ecology) for BMP monitoring.
* In the United States, there are three distinct climates that influence the nature and amount of rainfall occurring on an annual basis. Humid watersheds are defined as those that receive at least 40 inches of rainfall each year, Semi-arid watersheds receive between 20 and 40 inches of rainfall per year, and Arid watersheds receive less than 20 inches of rainfall per year. For this credit, 90% of the average annual rainfall is equivalent to treating the runoff from:
- (a) Humid Watersheds - 1 inch of rainfall
- (b) Semi-arid Watersheds - 0.75 inches of rainfall
- (c) Arid Watersheds 0.5 inches of rainfall.
Submittals (DESIGN):
Non-Structural Controls
- Provide list of Best Management Practices (BMPs), including a description of the contribution of each BMP and the percent annual rainfall treated.
Structural Controls
- Provide list of structural controls, including a description of the performance of the pollutant removal of each control and the percent annual rainfall treated.
- AND (For Projects With Special Circumstances - Either Compliance Path) - Provide an optional narrative to describe any additional comments or notes regarding special circumstances or considerations regarding the project's credit approach.
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